The field of this invention is "oral compositions" which herein means products intended for introduction into the oral cavity in such a manner as to contact exposed dental surfaces therein. Examples of such products are animal foods and beverages, chewing gums and oral hygiene products including mouth washes, prophylaxis pastes, topical solutions and dentifrices such as toothpastes, tooth powders, dental creams and the like.
Dental calculus, or tartar as it is sometimes called, is a deposit which forms on surfaces of teeth predominantly at or near the gingival margin. Supragingival calculus appears most heavily in areas near the orifices of the salivary ducts. Mature calculus contains an inorganic portion which is largely calcium phosphate arranged in a hydroxyapatite crystal lattice structure similar to that occurring in bone, enamel or dentine. Also typically present is an organic portion consisting of desquamated epithelial cells, salivary sediment, food debris, various types of microorganisms, etc.
As calculus develops, it becomes white or yellowish unless stained or discolored by some extraneous substance. In addition to being undesirable from an esthetic standpoint, mature calculus deposits are sources of irritation of the gingiva and thereby a contributing factor to gingivitis and other diseases of the supporting structures of the teeth, the irritation decreasing the resistance of tissues to endogenous and exogenous organisms.
Periodic mechanical removal of this material by a dentist is routine dental office procedure. There have also been proposed a number of chemical agents for calculus removal. For example, alkali metal and ammonium diglycolates and diglycolates of organic bases such as urea, guanidine or ethanolamine are suggested for that use in U.K. Pat. No. 995,330 issued June 16, 1965 to R. A. Oetker. In French Pat. No. 2,108,827 published May 26, 1972 it is said that the calcium ion-sequestering capability of sodium gluconate can be used for removal of tartar from the teeth. In U.S. Pat. No. 1,516,206 issued Nov. 18, 1924 to C. Pfanstiehl it is said that a tartar solvent effect is provided by use of an aqueous solution of a lactone or anhydride of a weak organic hydroxy acid, e.g. galactonic acid, together with a weak organic acid such as maleic or citric acid, and it is taught in U.S. Pat. No. 3,429,963 issued Feb. 25, 1969 to L. Shedlovsky that dental calculus can be removed by use of dental preparations containing a hydrolyzed copolymer of ethylene and maleic anhydride having an average molecular weight of at least about 1500.
In some instances, chemical agents have been said to be capable of retarding calculus formation. For example, in U.S. Pat. No. 3,429,963 it is disclosed that a reduction in calculus formation was observed in rats when the drinking water given to the rats contained 1% of a hydrolyzed copolymer of ethylene and maleic anhydride. Another polymer, i.e., a polyester of a polycarboxylic acid having three or more carboxyl groups and a polyalkylene ether having at least two hydroxyl groups, is described as a calculus retarding agent in U.S. Pat. No. 3,542,917 issued Nov. 24, 1970 to A. M. Schwartz et al. In U.S. Pat. No. 3,920,837 issued Nov. 18, 1975 to M. Schmidt-Dunker et al it is said that tartar formation can be reduced by cyclohexanehexacarboxylic acid or its water-soluble salts, and in U.K. Pat. Nos. 1,373,001 and 1,373,003 issued Nov. 6, 1974 to R. Hoyles et al it is said that calculus can be reduced by use of a dentifrice containing a sparingly water-soluble zinc salt, e.g. zinc citrate. Various phosphorous compounds such as, e.g., ethane-1-hydroxyl-1,1-diphosphonic acid (hereinafter EHDP) have also been proposed for such use in U.S. Pat. No. 3,488,419 issued Jan. 6, 1970 to H. W. McCune et al.
Some of the chemical agents heretofore proposed for calculus removal or retardation contain functional groups of uncertain effect on animals in terms of toxicity, side effects, etc. Certain other kinds of compounds containing only carbon, hydrogen, oxygen and possibly pharmaceutically acceptable cations are believed essentially free from such uncertainty and therefore preferable for use in oral compositions. Also desirable for present purposes are compounds of relatively simple structure and low molecular weight, as well as compounds which can be prepared without resort to a polymerization process. Accordingly, oral compositions containing compounds which meet those criteria and substantially inhibit dental calculus formation are highly desirable, and it is an object of this invention to provide such compositions. Another object is a method for inhibiting dental calculus formation by use of such compositions. Other objects will be apparent from the following disclosure in which percentages are by weight except where otherwise noted.